A disc brake has been hitherto employed as a braking device for a railway vehicle. As the disc brake, a railway wheel (hereinafter, also simply “wheel”) with brake discs (hereinafter, also simply “discs”) configured so that the discs are mounted on both side surfaces of the wheel respectively is frequently used.
FIG. 1 is a cross-sectional view of an ordinary wheel with discs. The wheel with discs shown in FIG. 1 is configured to include a wheel 1, a pair of discs 2 each in the form of a doughnut disc, and bolts 3 and nuts 4 for fastening these discs 2. A front surface of each of the paired discs 2 serves as a frictional surface 2e, and a plurality of cooling fin portions 2a are formed radially on a rear surface of the disc 2. Bolt holes 1b and 2b into which the bolts 3 are inserted are formed in a flat web 1a of the wheel 1 and the discs 2, respectively. The paired discs 2 of the wheel with discs are arranged to face each other across the web 1a of the wheel 1, and the discs 2 are fastened to the wheel 1 by the bolts 3 inserted into the bolt holes 1b and 2b and the nuts 4 in a state in which the cooling fin portions 2a are in contact with the web 1a of the wheel 1.
At a time of assembling the wheel with discs configured as described above, the entry of a foreign object between the wheel 1 and each disc 2 should be avoided. If such a thing occurs, the disc 2 undulates to follow the rotation of the wheel 1 while the railway vehicle is running since the disc 2 is attached obliquely to the wheel 1 with discs 2. If the undulation of the disc 2 is extremely large, then the contact state between the frictional surface 2e of the disc 2 and a brake lining becomes unstable during braking, and braking performance possibly degrades. Owing to this, it is necessary to make management of the height-direction undulation of the discs 2 mounted on the wheel 1 in the wheel with discs, and the measurement of the undulation of the frictional surface 2e of the disc has been hitherto carried out.
The measurement of the undulation of the frictional surface 2e of the disc in the wheel with discs has been hitherto made manually using a dial gauge with a lug fixed to a dedicated gauge stand. That is, in a state in which the wheel with discs is mounted horizontally on a measurement table, the gauge stand is arranged on a rim's surface 1e of the wheel on an upper surface side with the rim's surface 1e set as a reference surface while contacting a gauge head of the gauge with the frictional surface 2e of the disc 2 on the upper surface side of the wheel. From this state, while attention is paid to the index of the gauge, the gauge stand is made to slide on the rim's surface 1e by one or more rounds, and maximum and minimum scales of fluctuations in the gauge index are read. The difference between both of the read scales is calculated manually and the calculated value is grasped as the undulation of the frictional surface 2e of the disc.
If the undulation of the frictional surface 2e of the disc on a lower surface side is to be measured, then the wheel with discs is vertically inverted by a crane or a special inverting machine, the frictional surface 2e of the disc on the lower surface side is re-arranged on the upper surface side, and then the undulation is measured by the dial gauge similarly to the above. The reason for the rearrangement is difficulty to slide the gauge stand on the rim's surface 1e turned downward and to read the gauge index if the measurement target disc 2 is kept arranged on the lower surface side.